Calibration of oblique-incidence reflectivity difference for label-free detection of a molecular layer

Abstract

Oblique-incidence reflectivity difference (OI-RD) is a form of polarization-modulation ellipsometry that measures properties of thin films on a solid surface through the change in polarization state of light upon reflection from the surface. The measurement accuracy depends on the precision of the phase modulation amplitude and azimuthal alignments of key polarizing optical elements and, thus, requires careful calibration. In the present work, we describe robust methods of such calibrations that enable precise determination of the modulation amplitude and static retardation of a phase modulator and azimuths of key polarizing optics in an OI-RD system.

Fast Focal Point Correction in Prism-Coupled Total Internal Reflection Scanning Imager Using an Electronically Tunable Lens

“…An oblique-incidence reflectivity difference (OI-RD) scanning microscope is an ellipsometry-based biosensor. It is capable of detecting a biomolecular microarray with tens of thousands of features on a solid support [ 20 , 21 , 22 , 23 , 24 ]. To take advantage of an electrically tunable lens, we develop a prism-coupled OI-RD scanning microscope, as shown in Figure 1 .…”

“…To take advantage of an electrically tunable lens, we develop a prism-coupled OI-RD scanning microscope, as shown in Figure 1 . The microscope characterizes the thickness, d, of a molecular layer through the change in phase difference between the p- and s -polarized components of the reflected light beam caused by such a layer [ 20 , 22 ]: and represent the phase difference between the p- and s -polarization from the bare solid surface and from the solid surface covered with the molecular layer, respectively. The wavelength λ is 632.8 nm for the He-Ne laser used in this microscope.…”

Analysis of Fluid Replacement in Two Fluidic Chambers for Oblique–Incidence Reflectivity Difference (OI-RD) Biosensor

“…To address this challenge, we utilized COMSOL Multiphysics (version 6.0), a simulation software, to study the minimal liquid volume and optimal flow rate for two types of fluidic chambers in oblique–incidence reflectivity difference (OI-RD) biosensors. OI-RD is a label-free technique that utilizes fluidic chambers to measure biomolecular interactions in solutions [ 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. In our study, we examined the effects of flow rate, positions on the substrate surface bearing samples, and depth of the chamber on the required volume for complete fluidic replacement.…”